How to Select the Right Linear Bushings for Your Application

A linear ball bushing is a type of linear bearing, although the names are often interchangeable. Linear ball bushings are mechanical components used in linear motion systems to facilitate smooth and precise movement. These components are typically mounted on a linear shaft and provide support and low-friction guidance. In this guide, we’ll take a closer look, covering:

• Types of linear bushings
• Factors to consider in linear bearings selection
• Load capacity analysis for linear bushings
• Bushing material considerations
• Shaft compatibility with linear bearings
• Mounting and installation considerations for linear bearings

Types of linear bushings

A linear bushing or linear bearing, consists of an outer housing with an inner part that contains rows of ball bearings or rolling elements. These rolling elements circulate within the housing, reducing friction and allowing the linear shaft to move smoothly and accurately along its length. 

Linear bushings are commonly used in a wide range of applications, including machinery, automation, robotics, and manufacturing, where precise linear motion is required. They help improve the efficiency and reliability of linear motion systems by reducing wear and friction between moving components. 

Our range is composed of a housing with a row of 4-6 round ball circuits with an operating temperature range of -20°C to +120°C dependent on the makeup of the bearing. They’re for use with hardened shafts. Linear-bearing applications typically include automation systems, CNC machines, and manufacturing processes.

They belong to tolerance class h6, which means their tolerance is tight. You can learn more about tolerance class in our guide, How to Select the Ideal Linear Shaft for Your Application.   

Browse our entire range of Linear Bushings

Factors to consider in linear bearings selection

Choose linear bearings that align with your motion system, taking into account the factors below. We’ll take a closer look further on at the points that need more explanation. 

Load-Carrying Capacity: Assess the maximum axial and radial loads that the linear bearings will encounter in your specific application. Ensure that the chosen bearings have a capacity that exceeds the expected loads.
    
Load Type: Consider the nature of the load, whether it’s primarily axial, radial, or a combination of both. Different linear bearing types are tailored to excel in specific load orientations.
    
Speed and Acceleration: Evaluate the required speed and acceleration parameters for your linear motion systems. Some linear bearings are optimised for high-speed applications, while others are designed for slower, heavy-load scenarios.
    
Precision and Accuracy: Determine the level of precision and accuracy demanded by your linear-bearing applications. Precision bearings, with their tighter tolerances and reduced play, are indispensable for high-precision tasks. 
    
Environmental Conditions: Account for environmental factors, such as exposure to moisture. Opt for bearings capable of withstanding the conditions specific to your linear-bearing applications.
    
Shaft Compatibility: Verify that the selected linear bearings are compatible with the material, dimensions, and surface finish of the shaft or rail. Proper compatibility ensures smooth and efficient operation.
    
Lubrication: Define the lubrication method and frequency required for your application. Some bearings come pre-lubricated, while others may need periodic lubrication. Consider maintenance needs and susceptibility to contamination.
    
Sealing and Protection: Assess whether your application warrants additional sealing or protection to prevent the ingress of dust, debris, or moisture into the bearing. Sealed or shielded bearings are suitable for harsh environments.
    
Service Life: Calculate the expected service life of the linear bearings based on operating conditions and manufacturer-provided data. Opt for bearings with an adequate lifespan for your application.
    
Noise and Vibration: Evaluate acceptable noise and vibration levels for your application. Some bearings are engineered for quieter and smoother operation.

Load capacity analysis for linear bushings

Load capacity analysis for linear bushings is a fundamental step in preventing premature failure, ensuring the longevity of linear motion systems, and meeting the performance requirements of specific applications. Engineers and designers must carefully consider these factors during linear-bushing selection to ensure reliable and efficient operation. 

Types of Loads: Linear bushings typically encounter two primary types of loads:

• Axial Load: This refers to the force applied along the linear bushing's axis, running parallel to its length. Axial loads are the primary focus of linear bushing design and analysis.
• Radial Load: Although linear bushings are primarily designed for axial loads, some may have limited tolerances for radial loads, which are forces applied perpendicular to the bushing's axis.

Static and Dynamic Loads: The analysis of linear-bearing load capacity encompasses both static and dynamic loading conditions:

• Static Load Capacity: This represents the maximum axial load that a linear bushing can endure without suffering permanent deformation or damage when at rest. Manufacturers typically specify this capacity, which is relevant for linear-bearing applications involving stationary or slowly moving loads.
• Dynamic Load Capacity: This signifies the maximum axial load that a linear bushing can withstand during motion, considering factors like speed, acceleration, and the number of cycles it can endure before exhibiting signs of wear or failure.

Load Distribution: In practical applications, loads are seldom uniformly distributed along the length of the linear bushing. Linear-bearing load capacity analysis involves considering how loads are distributed across the bushing and calculating the maximum load that specific sections of the bushing may experience.

Environmental Conditions: Temperature, humidity levels, and exposure to contaminants can influence linear-bearing load capacity. Harsh environmental conditions can potentially reduce a linear bushing's ability to carry loads effectively.

Lubrication: Proper lubrication is essential to minimise friction and reduce wear within linear bushings. Insufficient or incorrect lubrication can lead to reduced load-carrying capacity and a shortened service life.

Material Selection: The choice of materials for the components of the linear bushing, including the outer shell and the ball or roller elements, significantly impacts load capacity. Material selection should align with the specific load and environmental conditions of the application.

Alignment and Mounting: Proper alignment and secure mounting of the linear bushing are critical to ensure even load distribution and maintain the bushing within its specified load capacity.

Safety Factors: It is common practice to apply a safety factor to the calculated linear-bearing load capacity to provide a safety margin in the design. This accounts for uncertainties in load estimation, variations in operating conditions, and the potential for unexpected overloading.

Bushing material considerations

Selecting the appropriate bushing material is critical. The choice of material should take into account various factors to ensure optimal performance and longevity. 

Load and Load Type

• Consider the magnitude and direction of the loads the bushing will encounter. Axial (along the bushing's axis) and radial (perpendicular to the bushing's axis) loads should be assessed.
• Determine whether the loads will be static or dynamic. Dynamic loads involve continuous motion, which can lead to increased wear and heat generation.

We recommend: Steel, and composite materials generally offer excellent load-bearing capabilities for both axial and radial loads. Steel is particularly strong and suitable for heavy loads.

Environmental Conditions

• Evaluate the operating environment, including temperature, humidity, and exposure to chemicals, moisture, or corrosive substances. Some materials offer better resistance to environmental factors than others.
• In outdoor or extreme conditions, use materials with corrosion-resistant coatings or stainless steel bushings.

We recommend: Stainless steel is often a preferred selection for challenging environmental conditions due to its resistance to corrosion. Additionally, plastic materials also exhibit corrosion resistance.

Speed and Friction

Consider the speed at which the bushing will operate. High-speed linear-bearing applications typically need materials that minimise friction and heat generation.

• The coefficient of friction of the bushing material can affect the system's efficiency and power consumption.

We recommend: Materials with inherent self-lubrication properties, such as PTFE and POM, are highly suitable for high-speed applications. This is because they effectively minimises both friction and heat generation. 

Wear Resistance

• Assess the potential for wear due to repeated motion and contact with other components. Materials with excellent wear resistance can prolong the bushing's service life.
• Consider materials with self-lubricating properties or coatings that reduce wear.

We recommend: POM is known for its excellent wear resistance. This property is crucial in linear bushings, where constant sliding and contact between moving parts occur. POM's wear resistance ensures that the bushings have a long service life, even under demanding conditions.

Shock and Vibration

• If the application involves shock or vibration, choose materials that can absorb or dampen these forces to prevent premature failure or damage.
• Composite materials or elastomeric bushings may be suitable for shock-absorbing applications.

We recommend: Elastomers, such as rubber, excel in absorbing shocks and damping vibrations. They’re suitable for linear-bearing applications with significant dynamic forces.

Shaft compatibility with linear bearings

The shaft and linear bearings must be compatible for a smooth linear motion. 

We’ve put together this table to show you the linear bearings compatible with specific linear shafts from our range: 

	Hardened Hollow Shafts	Hardened Stainless Shafts	Hardened Steel Shafts	Stainless AISI 303/316 Shafts	Aluminium Shafts
Closed, Open and Adjustable Linear Ball Bushes	✓	✓	✓
Double Complement Long Linear Ball Bushes	✓	✓	✓
Compact Linear Ball Bushes	✓	✓	✓
Front Flanged Ball Bushes	✓	✓	✓
Front Flanged Long Ball Bushes	✓	✓	✓
Centre Flanged Long Ball Bushes	✓	✓	✓
Superball Open and Closed Ball Bushings	✓	✓	✓
Ceramic Bearings				✓ Use with ceramic ball bearings	✓ Use with ceramic ball bearings

 

Browse our Linear Shafts

 

Mounting and installation considerations for linear bearings

Mounting and installation considerations for linear bearings are crucial to ensure their proper function, longevity, and performance in a linear motion system. Here are important factors to keep in mind when mounting and installing linear bearings:

Clean and Contaminant-Free Environment

Ensure that the installation area is clean and free from dust, dirt, debris, and other contaminants that can affect bearing performance and lifespan.

Proper Alignment

Achieve accurate alignment of the linear bearings and the shaft or rail to prevent binding or uneven loading. Misalignment can lead to premature wear and reduced system accuracy.

Shaft/Rail Straightness and Roundness

Verify that the shaft or rail is straight and round to prevent issues with linear- bearing operation. Ensure it meets the manufacturer's specified tolerances.

Lubrication

Apply the appropriate lubrication to the linear bearings as recommended by the manufacturer. Adequate lubrication reduces friction, minimises wear, and extends the bearing's service life.

Avoid Over-Lubrication

Take care not to over-lubricate, as excess lubricant can attract contaminants and lead to performance issues. Follow manufacturer guidelines for lubrication quantity and frequency.

Proper Fit

Ensure that the linear bearings fit correctly onto the shaft or rail. They should not be too loose or too tight. Follow manufacturer specifications for fit and clearance.

Correct Orientation

Install the linear bearings in the correct orientation as per the manufacturer's instructions. Bearings are often marked for their proper direction.

Evenly Distributed Load

Distribute the load evenly across multiple linear bearings if more than one is used in the system. Proper load distribution prevents overloading individual bearings.

Secure Mounting

Ensure that each linear bearing is securely mounted to the support structure or housing to prevent any movement during operation. Properly torque fasteners to the recommended specifications.

Check for Play or Binding

After installation, verify that there is no excessive play or binding in the linear bearings. This ensures smooth and consistent motion.

Maintenance Schedule

Establish a maintenance schedule for regular inspection, cleaning, and lubrication of the linear bearings to keep them in optimal condition over time.

Manufacturer Guidelines

Always refer to the manufacturer's installation instructions and guidelines specific to the linear bearings being used. These instructions may vary based on the linear bearing types.

Training and Expertise

If in doubt or if dealing with complex installations, talk to our experts for guidance.

Download free CADs and try before you buy

Free CADs are available for most solutions, which you can download. You can also request free samples (some exclusions apply) to ensure the product you’ve chosen is exactly what you need. 

If you need help with your linear bushing selection, our experts are always happy to advise you.

Request your samples or download free CADs now.

Questions?

Email us at sales@essentracomponents.co.uk or speak to one of our experts for further information on the ideal solution for your application 0345 528 0474.